/*************************************************************************
 *
 *   file		: MpqWavCompression.cs
 *   copyright		: (C) The WCell Team
 *   email		: info@wcell.org
 *   last changed	: $LastChangedDate: 2008-01-31 19:35:36 +0800 (Thu, 31 Jan 2008) $
 *   last author	: $LastChangedBy: tobz $
 *   revision		: $Rev: 87 $
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *************************************************************************/

using System;
using System.IO;

namespace MpqReader
{
	/// <summary>
	/// An IMA ADPCM decompress for Mpq files
	/// </summary>
	public class MpqWavCompression
	{
		private MpqWavCompression()
		{}

		private static readonly int[] sLookup =
		{
			0x0007, 0x0008, 0x0009, 0x000A, 0x000B, 0x000C, 0x000D, 0x000E,
			0x0010, 0x0011, 0x0013, 0x0015, 0x0017, 0x0019, 0x001C, 0x001F,
			0x0022, 0x0025, 0x0029, 0x002D, 0x0032, 0x0037, 0x003C, 0x0042,
			0x0049, 0x0050, 0x0058, 0x0061, 0x006B, 0x0076, 0x0082, 0x008F,
			0x009D, 0x00AD, 0x00BE, 0x00D1, 0x00E6, 0x00FD, 0x0117, 0x0133,
			0x0151, 0x0173, 0x0198, 0x01C1, 0x01EE, 0x0220, 0x0256, 0x0292,
			0x02D4, 0x031C, 0x036C, 0x03C3, 0x0424, 0x048E, 0x0502, 0x0583,
			0x0610, 0x06AB, 0x0756, 0x0812, 0x08E0, 0x09C3, 0x0ABD, 0x0BD0,
			0x0CFF, 0x0E4C, 0x0FBA, 0x114C, 0x1307, 0x14EE, 0x1706, 0x1954,
			0x1BDC, 0x1EA5, 0x21B6, 0x2515, 0x28CA, 0x2CDF, 0x315B, 0x364B,
			0x3BB9, 0x41B2, 0x4844, 0x4F7E, 0x5771, 0x602F, 0x69CE, 0x7462,
			0x7FFF
		};
		
		private static readonly int[] sLookup2 =
		{
		    -1, 0, -1, 4, -1, 2, -1, 6,
		    -1, 1, -1, 5, -1, 3, -1, 7,
		    -1, 1, -1, 5, -1, 3, -1, 7,
		    -1, 2, -1, 4, -1, 6, -1, 8
		};

		public static byte[] Decompress(Stream Data, int ChannelCount)
		{
			int[] Array1 = new int[] {0x2c, 0x2c};
			int[] Array2 = new int[ChannelCount];

			BinaryReader input = new BinaryReader(Data);
			MemoryStream outputstream = new MemoryStream();
			BinaryWriter output = new BinaryWriter(outputstream);
			
			input.ReadByte();
			byte shift = input.ReadByte();
			
			for (int i = 0; i < ChannelCount; i++)
			{
				short temp = input.ReadInt16();
				Array2[i] = temp;
				output.Write(temp);
			}

			int channel = ChannelCount - 1;
			while(Data.Position < Data.Length)
			{
				byte value = input.ReadByte();

				if (ChannelCount == 2) channel = 1 - channel;
				
				if ((value & 0x80) != 0)
				{
					switch (value & 0x7f)
					{
						case 0:
							if(Array1[channel] != 0) Array1[channel]--;
							output.Write((short)Array2[channel]);
							break;
						case 1:
							Array1[channel] += 8;
							if(Array1[channel] > 0x58) Array1[channel] = 0x58;
							if (ChannelCount == 2) channel = 1 - channel;
							break;
						case 2:
							break;
						default:
							Array1[channel] -= 8;
							if(Array1[channel] < 0) Array1[channel] = 0;
							if (ChannelCount == 2) channel = 1 - channel;
							break;
					}
				} else
				{
					int temp1 = sLookup[Array1[channel]];
					int temp2 = temp1 >> shift;

					if ((value & 1) != 0)
						temp2 += (temp1 >> 0);
					if ((value & 2) != 0)
						temp2 += (temp1 >> 1);
					if ((value & 4) != 0)
						temp2 += (temp1 >> 2);
					if ((value & 8) != 0)
						temp2 += (temp1 >> 3);
					if ((value & 0x10) != 0)
						temp2 += (temp1 >> 4);
					if ((value & 0x20) != 0)
						temp2 += (temp1 >> 5);

					int temp3 = Array2[channel];
					if ((value & 0x40) != 0)
					{
						temp3 -= temp2;
						if(temp3 <= short.MinValue) temp3 = short.MinValue;
					} else
					{
						temp3 += temp2;
						if(temp3 >= short.MaxValue) temp3 = short.MaxValue;
					}
					Array2[channel] = temp3;
					output.Write((short)temp3);
					
					Array1[channel] += sLookup2[value & 0x1f];

					if(Array1[channel] < 0) 
						Array1[channel] = 0;
					else 
						if(Array1[channel] > 0x58) Array1[channel] = 0x58;
				}
			}
			return outputstream.ToArray();
		}
	}
}
